RSC Mechanochemistry最新文献

A reagent-free, catalyst-free, sustainable methodology was developed for fast and effortless synthesis of quinoxalines by mixing and homogenizing the substrates in a mini cell homogenizer. The mechanochemical agitation between several aromatic (and heteromatic) 1,2-diamines and various 1,2-dicarbonyl compounds with stainless steel balls in simple polypropylene vials at 4000 rpm afforded the corresponding quinoxalines and pyrido[2,3-b]pyrazines via cyclocondensation within a few minutes mostly in quantitative yields. The use of an equimolar ratio of substrates and complete conversion ensured quick access to quinoxalines in a sufficiently pure form offering the additional advantages of a work-up free and purification-free approach. As eliminated water molecules in the process do not contribute to waste, the E-factor of the method is practically zero.

The failure of interfaces between polymers and inorganic substrates often leads to deteriorated performance, as is the case for polymer matrix composites. Interfacial mechanophores (iMPs) have the potential to fluorescently measure interfacial failures. Spirolactam-based mechanophores are of interest due to their readily available synthetic precursors and compatibility with epoxy matrices. In this work, spirolactam is covalently bound at the interface of silica surfaces and epoxy, chosen due to the industrial relevance of glass fiber composites. The iMPs are mechanically activated through uniaxial tension applied to the composite while the resulting fluorescent response is observed in situ with a confocal microscope. Due to their real time sensing capabilities, iMPs are a promising technique to measure interfacial failures in composite materials more easily than with traditional optical microscopy techniques.

In this paper, we introduce a novel planetary ball mill device featuring an interchangeable speed ratio, allowing users to manually adjust this parameter to suit the needs of each reaction. The device's modular design offers unprecedented control over the kinetic energy input, enabling enhanced reaction efficiency, selectivity, and precision.

A mechanochemical approach was utilized for the synthesis of naloxone covalently linked poly(lactic acid) and nanoparticles. This preparation was achieved using lactide as a monomer in anionic ring opening polymerization, naloxone as a drug initiator, and CHCl₃ to perform liquid-assisted grinding. This process resulted in the direct preparation of a naloxone nanoparticle with a drug loading of ∼8.3% w/w and nanoparticles around 600 nm. These findings underscore the promise of mechanochemistry in developing drug delivery systems.

The prediction of the phase behaviour of a mixture of solid components when they come into contact is of high interest in fast growing research fields such as mechanochemistry and deep eutectic solvents (DESs). This paper provides a friendly predictive tool (PoEM, i.e. Predictor of Eutectic Mixtures), along with some guidelines and quantitative references, to quickly estimate the variation in the melting point due to the mixture of reactants for a mechanochemical process. An empirical model that estimates the ideal eutectic point and includes deviation from ideality based on intermolecular interactions is presented here, allowing for the design of synthetic procedures for solvent-less cocrystallization processes. PoEM calculations are validated by comparing the prediction with experimental behaviour of a number of mixtures with a low melting eutectic mixture. Finally, as a working example we consider how to identify coformers for the synthesis of a cocrystal containing thymol such that the cocrystallization would proceed through the formation of a metastable liquid phase.

The milled-Li_1.2Cr_0.4Mn_0.4O₂ (milled-LCMO) cathode, a promising material for next-generation Li ion batteries, is prepared by dry ball-milling of layered rocksalt-type Li_1.2Cr_0.4Mn_0.4O₂ (layered-LCMO) obtained by solid-state synthesis. Despite undergoing ball-milling treatment, resulting in separation into Cr-rich and Mn-rich phases along with Li₂O, milled-LCMO still exhibited a reversible capacity of 277 mA h g⁻¹ at a rate of 16 mA g⁻¹. However, it was also revealed that its cyclability was poor due to the contribution of oxygen redox in the charging process. On the other hand, layered-LCMO exhibited better cyclability because charge and discharge reactions proceeded only through the Cr redox. The thermally treated Li_1.2Cr_0.4Mn_0.4O₂ was prepared as a cathode material that combines the favorable properties of these two materials. In fact, each thermally treated sample showed a larger reversible capacity than the layered-LCMO obtained by the solid-phase method, and the cyclability recovered as the heat treatment temperature increased.

Antimony powder is transformed into 2D antimonene in a vortex fluidic device (VFD) at ambient conditions, depending on the choice of solvent (optimised as a 1 : 1 mixture of isopropyl alcohol and dimethylformamide) and the operating parameters of the microfluidic platform which houses a rapidly rotating quartz tube inclined at +45°. It is hypothesised that the Coriolis force from the hemispherical base of the tube, as typhoon like high-shear topological fluid flow down to submicron dimensions, generates localised heating at the quartz interface. This melts the antimony powder (m.p. 630.6 °C) in situ which crystallizes in the β-phase, with semi-conducting antimonene a few layers thick, and demonstrating novel photoluminescence.

An intriguing technique for crystal engineering is mechanochemistry, which frequently yields various solid forms (salts, cocrystals, polymorphs, etc.) that are challenging to acquire using traditional solution-based approaches. However, generating new and potentially beneficial solid forms remains an ongoing task in this field. Moving forward in this demanding arena, several molecular adducts (salts and salt polymorphs) of the model drug ensifentrine (ENSE) with different GRAS (generally recognized as safe) co-former were synthesised for the first time using a mechanochemical technique, followed by a slow evaporation crystallisation procedure. All the newly obtained solid forms were characterized by employing single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Crystal structure analysis verified salt generation, revealing proton transfer from the carboxylic acid group of salt formers to the mesitylimino nitrogen atom of ENSE. Additionally, the phase transition behaviour of the produced salt polymorphs was examined through variable temperature PXRD (VT-PXRD) analysis. Furthermore, a detailed investigation of the physicochemical features of these recently produced entities was carried out, and their solubility in pH 1.2 and pH 7 environments was examined. Results demonstrate that, as compared to the parent drug, the binary adduct's solubility rate significantly increased at pH 7. Moreover, a thorough examination of the residue recovered after solubility confirmed that the majority of the molecular adducts were stable at pH 7 and did not show any phase change or dissociation, whereas at pH 1.2, the majority of the adducts were stable, except for those generated with malonic acid, which moved to a new stable form—a comprehensive study revealed that it was converted into ENSE·Cl salt. To the best of our knowledge, this is the first study to investigate various forms of ENSE, demonstrating that mechanical energy can be employed as a powerful control parameter to produce novel solid forms with superior physicochemical features. We hope that the current discovery will offer a valuable outlook prior to ENSE drug formulation.

Mechanochemistry is increasingly recognized for its sustainability, environmental benefits, and efficiency in synthesizing a wide array of chemicals and materials. This research focuses on advancing our understanding of the factors that influence mechanochemical processes, which remains limited despite the broad application of these techniques in industry and research. Specifically, this paper explores the impact of mass transfer—a parameter previously underexplored in the context of mechanochemistry—on the outcome of chemical syntheses performed without solvents, thus avoiding the use of environmentally harmful substances and complex purification steps. This study introduces a novel multi-functional ball-mill medium design that enhances mass transfer, promotes more uniform kinetic energy distribution and material treatment, and increases overall synthesis efficiency. By analyzing the products of allotrope conversion, co-crystallization, and size reduction, we demonstrate how our new design enhances mechanochemical reactions. The findings indicate that adjusting the geometry of the milling media can significantly influence the chemical transformation processes. This advancement not only contributes to a deeper comprehension of mechanochemical synthesis but also opens avenues for more controlled and scalable production methods. The research underscores the importance of considering mass transfer in developing more effective mechanochemical technologies, paving the way for future innovations in this green chemistry field.

Thioamidation of various classes of carboxamide substrates with Lawesson's reagent under liquid-assisted mechanical activation for the synthesis of relevant building blocks including aromatic thioamides, thiopeptides, thiolactams, and thioenones is described. A thorough analysis of the effect of the specific material of milling jars and milling balls was carried out. The effect of different additives for liquid-assisted grinding (LAG) and the potential of the synthetic protocol for scale-up were explored. The simple and mild reaction conditions involved in this solvent-minimized mechanochemical protocol proved rather effective with a wide variety of substrates. Comparison with the corresponding reactions in solution shows comparable or better yields under mechanochemical activation. Ex situ powder X-ray diffraction (PXRD) monitoring with analysis at multiple points was performed in order to compare the diffraction patterns of reagents and products, to detect potential morphological changes of the reagents induced by milling prior to the reaction, and to perceive the occurrence of phase transitions during the mechanochemical reaction.